Device for measuring subsurface temperatures of liquid bodies, useful for determining optimum fishing locations

ABSTRACT

The invention provides a fishing lure useful for measuring water temperature at a certain depth. The lure includes a temperature sensing part embedded in an insualting matrix part which provides a useful heat flow pattern. After being exposed to water of a certain temperature the temperature sensing part will thermally equilibrate to that temperature after a period of time. The device will then hold this temperature reading even while being briefly exposed to mediums of different temperatures, such as exposing the lure to air or water of varying temperature, and will allow accurate readings of the original temperature. The fishing lure appears to exploit the difference in thermal conductivities of air versus other media, such as water or slurries.

This is a division of application Ser. No. 046,782, filed May 7, 1987,now U.S. Pat. No. 4,883,365.

BACKGROUND OF THE INVENTION AND DISCUSSION OF THE PRIOR ART A) Problemsin General Temperature Measurement of Liquids

A method for readily measuring the temperature of liquids and slurriesat positions other than at the surface of the liquid has been elusive.An example will serve to illustrate this problem.

Consider the difficulties in measuring the water temperature at thebottom of a lake fifty feet deep. Since thermometers, such as thosebased on liquid in glass, liquid crystals or bimetallic strips rapidlyrespond to temperature changes, they cannot be used to make thismeasurement. When these devices are lowered to the bottom of the lakeand then raised to the surface for reading they quickly lose thetemperature reading of the water at the bottom of the lake. Thetemperature recorded by these devices may reflect that of theintervening water or even of the air above the lake. In any event therecorded value is unreliable and does not reflect the temperature at thebottom of the lake.

The usual method for making such a temperature measurement is to lower athermocouple to the bottom of the lake and to read the temperature usinga suitable meter and power supply. This method is cumbersome and doesnot lend itself to ready and repeated use.

Besides being expensive, the equipment has the usual drawbacksassociated with electrical contacts, long lengths of wire and usefullife of electronic equipment at high humidity conditions. In addition,many of these environments can be very demanding in terms of physicalstress (e.g. fishing boats) and corrosiveness (e.g. brines),particularly in windy conditions.

Another problem area of temperature measurement is with slurrries wherethe suspended solids block the view of the temperature scale on thethermometer. Vats of paint, sewage, lakes of black brine, and riversloaded with silt are some examples of these types of situations.

In these instances it is desirable to remove the thermometer from theliquid for reading. Cleaning of the thermometer may even be necessary.Normal thermometers lose their readings in just a few seconds on removalfrom such slurries.

Another problem area of temperature measurement is the area of corrosiveand/or fuming liquids. Thermocouples are readily attacked by manycorrosive liquids and strong fumes, such as acids, ammonia and caustic.Intensely smelling or volatile poisonous chemicals often discourage orprevent a person from making a close approach for a temperaturemeasurement.

B) Problems in Determining Optimum Fishing Waters Based on Temperature

It has been well established that fish seek out waters of a specifictemperature, herein called the optimum temperature. Different species offish prefer different temperatures. The range of preferred temperaturesis from about forty degrees Fahrenheit for fish such as certain trout toabout eighty degrees for certain tropical fish. Below this range fish donot take bait because they simply are not moving and feeding since theyare cold blooded. Above this range the water is too warm and can be lowin oxygen. Fish will not remain in this warm water for any significantlength of time. This situation parallels that of humans who prefer thewell known "comfort zone" of 72-78 degrees Fahrenheit. The effects oftemperature on the habits of fish are an important part of Limnology,which is "the study of the behavior of lakes and other inland waters andof the various physical, chemical, meteorological, and biologicalconditions existing in them".

Temperatures of natural bodies of water are known to vary widely withthe seasons, springs, currents, winds, amount of sunshine, time of dayand ice coverage. This helps to make fishing exceedingly difficult sincethe fish move frequently in response to the ever changing watertemperatures. Very often fisherman will spend hours trying to catch fishin waters which would not be expected to contain fish based on the watertemperatures.

Fishing for crappie in the early spring is a classic example of thissince the fish are feeding but are hard to find because there is stillso much cold water present from the previous winter. Early spring warmair may mislead the fisherman since the water may still be too cold forcrappie. Summer fishing conditions often create a similar situation inthat most of the water is too warm for fish. This forces the fish intohard-to-find small pockets of cool water. Surface temperature readings,although easy to measure, are usually useless since they only indicatewhether or not fish can be expected at the surface of the body of water.Fish are not normally close to the surface.

Normal thermometers simply respond too quickly to temperature to allowtheir use at other depths. The temperature readings of normal liquid inglass, liquid crystal and coiled spring type thermometers change quicklyand significantly before they can be brought to the surface for reading.What is needed is a simple and reliable method to record watertemperature at any depth. The present invention resolves this key need.

Although the temperature preferences of fish have been known for a longtime it has not been possible for most fishermen to take advantage ofthis understanding since a good method has not been available to makethe necessary measurements.

Devices representing the prior art in the area of water temperaturemeasurement for the purpose of identifying optimum fishing waters areavailable through fishing equipment distributors such as E. HILLE CO.(page 29 of catalog No. 49) NETCRAFT CO. (page 15 of catalog #84-B) andCABELA'S (pages 80 and 81 of SPRING 1984 catalog). None of these devicesis similar to the present invention. The addresses of these companiesrespectively are: CABELA'S, 812 Thirteenth Ave, Sidney, Nebr. 69160; E.HILLE CO., P.O. Box 996, Williamsport, Pa. 17703; and THE NETCRAFT CO.,2800 Tremainsville Rd., Toledo, Ohio 43613. A discussion of this priorart follows. Item #1D-10R9A on page 15 of the NETCRAFT CO. catalog anditem #203-100-000 on page 80 of CABELA'S catalog are similar. These twodevices consist of a liquid alcohol in glass type thermometer and apressure sensitive metal valve. These devices function in a totallydifferent manner than the device in the current invention. These devicesmeasure temperature using a typical glass thermometer encased in aplastic tube. The valve allows water to enter the tube in an amountproportional to the depth and then the thermometer inside the tube readsthe temperature of the water which entered the tube. This method oftemperature measurement is sensitive to use methods. Thereforesignificant care in handling the device is required to avoid erroneousreadings.

The device does not work in the important region from the surface downto about four feet since insufficient water enters the device to allow atemperature measurement. This is because of the low water pressure whichexists at these shallow depths.

In addition the need for the metal pressure valve provides a fastcooling (or warming) effect once the device is removed from the depth ofwater in which a temperature measurement has been made and when it ishandled or brought into the cool or warmer air.

Also, these devices become clogged with silt and mud when they strikethe bottom during and before a measurement causing an erroneous readingwhen too much water enters.

A key problem in the use of this type of device is that it cannot belowered past the depth to be measured since it would then allow too muchwater to enter. This results in erroneous depth and temperaturereadings.

Another problem with devices of this type is that fishermen rarely havethe capability to measure depth accurately. Normally the depth"measurement" is so many reel cranks from the bottom or from thesurface. Hence an absolute depth measurement is of little value to thefisherman.

These devices also require resetting before reuse which makes their usefor repetitive measurements less attractive and slow.

A second type of device in the prior art (CABELA'S, page80,#668-102-000) consists of a battery powered meter and thermocoupledetector and a thirty foot cord. This device suffers from being toocomplicated for routine use, too awkward to use, susceptible to foulingand corrosion by the humid environment of fishing waters, and limited inboth the depth and the information available to the user. It is alsoexpensive. In addition, it is difficult for the fisherman to reproducethe depth read by the device with bait since it is totally separate fromthe fisherman's rod and reel.

A third type of device in the prior art (CABELA'S page 81,#317-100-000)is merely a temperature gauge with a detector which fits onto the bottomof a boat on which the meter is mounted. Obviously this device only canmeasure the surface water temperature which is of little value indetermining where the waters are which are optimum for the type of fishbeing sought.

For example, on a lake in hot summer the fish will be at the thermoclinewhich could be anywhere from five to about thirty feet below the surfacedepending on the length of the hot spell and other factors. The devicewill only give the surface temperature of say 80 to 90 degreesFahrenheit which is of little value. This device is also very expensive.

The fourth type of prior art is the device offered by E. HILLE CO. (page29 of catalog No. 49, part No. 2015). This device is just a normalthermometer in a rugged case. It is only useful for measuring thesurface temperature of a body of water.

C) REFERENCES

1. a) "Fundamentals of Temperature , Pressure and Flow Measurements" byRobert P. Benedict, John Wiley and Sons Inc. (New York, 1969).

b) "Temperature Measurement" in the Encyclopedia of Chemical Technology,19,774 (Kirk-Othmer, 1978).

2. a) "The Fisherman's Encyclopedia" by Ira N. Gabrielson, Ed. Stackpoleand Heck (New York, 1950), pp 231-244.

b) Jerry Gibbs in Outdoor Life Nov. 1982 35.

c) "Bass Like it Hot", Outdoor Life July 1983 88.

d) "Survey of Marine Fishes of North Carolina" by Harden F. Taylor, TheUniversity of North Carolina press, 1951, pp 21-36.

e) "A History of Fishes" by J. R. Norman, Hill and Wang (New York,1963), pp 266-275.

3. a) "Liquid Crystals : The Fourth State of Matter" by Franklin DSaeva, Ed., Marcel Dekker Inc. (New York, 1983).

b) "Liquid Crystals" in the Encyclopedia of Chemical Technology, 14(Kirk-Othmer, 1978), 395ff.

c) "Liquid Crystals : A colorful State of Matter" by G. H. Brown and P.P. Crooker, Chem and Engin. News, Jan. 1983 24.

d) Physics Today 1982 35 25-73 (six review articles).

4. a) Modern Plastics Encyclopedia 1984-1985, McGraw Hill Inc. (NewYork).

b) Plastics Technology Annual Processing Handbook 1970-1971 16(10), BillPubl., 1970.

c) "Do It Yourself With Plastics" by Erich H. Heimann, Publ. E. P.Dutton and Co. Inc. (New York, 1975).

II. SUMMARY OF THE INVENTION A) General Description

The invention disclosed herein is a device which is useful for themeasurement of temperature. The device is most useful for themeasurement of temperature in certain situations where the usualtemperature measurement methods either fail or would be very difficultto implement. The device is especially useful for the measurement oftemperature of liquids whose depth, color or composition maketemperature measurements of them difficult or impossible by normalmeans.

Examples of such difficult situations are water bodies such as lakes,rivers, oceans and streams at depths other than those at the surface orwithin reach. Other examples are municipal drinking water tanks, tankertrucks bearing liquid cargo, underground gasoline or kerosene tanks,sewage treatment plants, oil and water wells, vats and tanks ofcorrosive or fuming liquids and slurries, fermentation broths, etc.

The invention is especially useful as an aid to fishing. The devicereadily and simply identifies which waters have the best chance ofcontaining fish. This connection is based on the scientific fact thatfish seek out water of optimum temperature. This optimum temperaturevaries with the type of fish. As will be described this variation isreadily provided for by the invention.

The device of this invention is composed of a temperature sensing partand a matrix part. As discussed below, the device may also contain othercomponents which serve to make the device more convenient to use.

The device of the invention consists of a temperature sensitive deviceimbedded in a matrix which provides a useful heat flow pattern.Apparently the device exploits the difference in the thermalconductivities of air versus other media, such as water or slurries, tofunction.

Plastics are the preferred matrix material for most applications. Theinsulating and hydrophobic properties of plastics appear to be importantalso. The chemical and solvent resistance of certain plastics canprovide additional useful variations.

Additional advantages of the device are that it is very simple to useand does not corrode or need batteries. It does not use wires or requireresetting or contain moving parts or have depth limitations. In additionit does not require installation or accessories and is very durable. Oneor more of these features make this invention a marked improvement overthe prior art.

B) Temperature Sensor

The temperature sensing part can be any of the well known stand alonedevices for measuring temperature such as liquid in glass, liquidcrystal ribbon, liquid-expansion or bimetallic strip. Even athermocouple can be used.

All of these devices are normally used in conjunction with numberedscales off which the temperature is read using the temperature sensingcomponent as a pointer. Thermocouples are usually used with analog ordigital meters. Thermometers using these temperature sensors are wellknown in the art. Temperature sensors based on liquid in glass,bimetallic strip and liquid expansion have been known for a very longtime.

The use of liquid crystals for the measurement of temperature is afairly recent occurrence even though liquid crystals have also beenknown for many years. The category of liquid crystals which are mostuseful for temperature sensors is well known in the art as thermotropicliquid crystals. Thorough discussions are available in the literature.Reference 3a which discusses their use in temperature measurement andreference 3b discusses the various categories and other classificationsof liquid crystals and references 3c and 3d which are concise reviews.

C) The Matrix

The second component of the device of this invention, the matrix, worksin conjunction with the temperature sensing component to produce theunique temperature measuring properties of this invention.

The matrix is preferrably a clear, hydrophobic and thermally insulatingmaterial of sufficient thickness to impart the desired temperatureresponse properties.

It is also preferable that this matrix has a specific gravity greaterthan the bulk density or specific gravity of the medium whosetemperature is to be determined.

The matrix can be made of glass or plastic or any combinations thereof.

The matrix is preferably a plastic since these are easier to mold andare more rugged than glass. Resins and the plastics prepared from themare described in the art.

Plastics which possess the above desired properties are the clear formsof ploycarbonate (PC), polymethylmethacrylate (PMMA or acrylic),polystyrene (PS), flexible polyvinyl chloride (fPVC), cellulose acetate(CA), cellulose triacetate (CTA), ethyl cellulose (EC), allyl polyesters(AP), cellulose acetate propionate butyrate (CAPB), nitrile (N),amorphous nylon such as semicrystalline Nylon 6 or random polymer ofNylon 12 with cycloaliphatic and aromatic comonomers, random Nyloncopolymers such as PA7030 (Upjon Co.). Transparent fluoroplastics suchas polychlorotrifluoroethylene (PCTFE) and polyvinyl fluoride (PVF),(the fluoroplastics are marginally transparent even in fairly thinlayers and are therefore not preferred).

Clear forms of polybutylene (PB), aromatic polyester (polyarylate),clear forms of alkyd polyester, polyethyene terephthalate polyester(PET), unsaturated polyester (UP), polyetherimide (PEI), transparenttypes of polyetheretherketone (PEEK), transparent types of high and lowdensity polyethylene (HDPE<LDPE), transparent types of linear lowdensity polyethlyene (LLDPE), ionomer polyethlyene (IPE), transparentforms of ethylene-acrylic acid (EAA) and ethlyene-methacrylic acid(EMAA), ethylene-ethylacrylate (EEA), ethylene-methacrylate (EMA),ethylene-vinylacetate (EVA), polymethyl pentene (PMP), polypropylene(PP) and crystal polystyrene (CPS). The translucent form of impactpolystyrene (IPS) is not preferred since it is translucent.

Butadiene-styrene (BS) (polymers can be blended with compatible lowtransparency or opaque resins such as general purpose PS and SAN inwidely varying ratios to obtain high clarity plastics ). Transparentforms of polyurethane (PU), vinylidene chloride polymers and copolymers(VDC), silicone, styrene-acrylonitrile (SAN), styrene-maleic anhydride(SMA) including terpolymers with butadiene, polysulfone, polyarylsulfoneand polyether sulfone. Epoxy resin (ER), urea formaldehyde (UF) andmelamine formaldehyde (MF) are also suitable.

Thermoset resins are preferred over thermoplastic resins when the higherprocessing temperatures required for thermoplastics cannot be toleratedby the temperature sensing component. Clear plastics are preferred overtranslucent ones.

It is sometimes possible to modify some opaque plastics bycopolymerization with another monomer or additive to make themtransparent. For example, transparent grades of ABS are made by usingmethyl methacrylate (MMA) as the fourth monomer. Modifications of thistype are considered to be obvious extensions of the prior art ofplastics processing.

Since plastics have a wide range of tolerances to solvents, andcorrosive liquids, sunlight, etc, these factors would necessarily haveto be taken into account in preparing a device for a specificapplication. These procedures would represent an optimization on theinvention.

In a similar manner, a plastic needs to be chosen with a melting pointabove any temperature the device might experience in a particularapplication. Of course the temperature range of the temperature sensingcomponent must be chosen according to the specific application also.

Some polymers could be made to function if a suitable transparent windowis provided so that the scale of the internal temperature sensingcomponent can be read. For example, such a window could be made of glassor a clear plastic.

Clear versions of flexible polyethylene (fPE) and high densitypolyethylene (HDPE) are useable also. However, since the specificgravity (0.92) of these two plastics is less than that of water (1.00)they would float on this liquid. A device made using these plasticswould need to be weighted with lead or by some other means if it isdesired to use the device in a water temperature measurement beneath thesurface of the liquid.

Since many organic liquids have specific gravities in the 0.7 to 0.8range, these plastics would be suitable for these liquids without anyneed for additional weight.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of step 1 of Method A used to prepare thetemperature sensing apparatus.

FIG. 2 is a side view of step 2 of Method A used to prepare thetemperature sensing apparatus.

FIG. 3A is a side view of step 1 of Method B used to prepare thetemperature sensing apparatus.

FIG. 3B is a side view of step 2 of Method B used to prepare thetemperature sensing apparatus.

FIG. 3C is a side view of step 3 of Method B used to prepare thetemperature sensing apparatus.

FIG. 3D is a side view of the final temperature sensing apparatusprepared according to Method B.

FIG. 4A is a top view of the lower section of the aluminum mold used toprepare the temperature sensing apparatus according to Method C.

FIG. 4B is a top view of the top section of the aluminum mold used toprepare the temperature sensing apparatus according to Method C.

FIG. 4C is a view of the temperature sensor insert used for preparingthe temperature sensing apparatus according to Method C.

FIG. 5 is a view of the finished temperature sensing apparatus accordingto Method C.

FIG. 6A is a side view of the mold used to prepare the temperaturesensing apparatus according to Method D.

FIG. 6B is a view of the temperature sensor insert used for preparingthe temperature sensing apparatus according to Method D.

FIG. 6C is a side view of the finished temperature sensing apparatusaccording to Method D.

FIG. 7 is a side elevation view of a fishing lure incorporating thepresent invention;

FIG. 8 is a side elevation view of the use of the present invention in atrap or net to catch fish.

FIG. 9 is a schematic side elevation view of the use of the presentinvention in connection with a trot line for catching fish.

D) Theory of Operation

The device comprises a temperature sensing element for temperaturemeasurement in a matrix of the proper amount.

It has been found that when a temperature sensitive element is imbeddedin a plastic matrix of sufficient thickness, an unexpected temperatureresponse pattern develops. When the device is immersed into water, forexample, the temperature can be seen to equilibrate within just a fewminutes. However, on removing the device from the water it does notchange its reading for a long time.

But if the device is inserted back into some water at a differenttemperature than the first it assumes this new temperature withinseconds or just a few minutes.

This property is useful for the age old problem of measuring thetemperature of water bodies at various depths. The device enables actualwater temperatures to be taken at any depth without the use ofcumbersome thermocouple wires or rapidly changing liquid filled glassthermometers or bimetallic strips.

Thus the present invention provides a reliable method for reading thetemperatures of the liquids in a wide variety of situations.

It is simple to use and can be used repeatedly. It readily provides amethod for measuring temperature in deep waters, slurries, corrosive oropaque liquids To make such measurements the device is merely lowered,using any suitable line or rod, into the medium whose temperature isdesired, such as the lake and opaque slurries referred to above. Thedevice is allowed to hang at the position where a temperaturemeasurement is wanted until thermal equilibration is attained This maytake from about thirty seconds to several minutes depending on the exactdesign of the device (see below). More time may be needed for very largedevices and very large temperature differences.

The device is then rapidly withdrawn from the medium and the temperatureat the depth where the thermal equilibration took place is read directlyfrom the device. The device will hold this temperature for at leastseveral minutes, again depending upon design This is plenty of time forthe user to record the temperature reading by visual observation.

Futhermore, the device is immediately ready for reuse without anyfurther preparation. It is a significant feature of the invention thatit readily thermally equilibrates in the medium being measured while atthe same time it holds this temperature long enough in the air for areading to be made.

Since temperature is a fundamental property of nature there is always aneed for improvements in its measurement. This invention is a new methodof temperature measurement. It enables the measurement of temperature insituations where the known methods either cannot be used or are verydifficult to implement. Thus this invention also addresses a key needsince temperature is a fundamental property of nature.

E) Application of the Invention To Fishing

The device is very useful for determining optimum fishing depths andlocations.

It can be used at any depth merely by letting it down into the waterattached to a line. In fact it is preferred that the device be loweredusing a normal fishing rod and reel. The exact depth in which themeasurement was taken is easily reproduced with bait since the number ofreel cranks up from the bottom or down from the surface are easilycounted and then reproduced.

The device can be used for both trolling and still fishing. It is usefulin both fresh and salt water. It provides reliable information even inthe presence of undercurrents, springs, and thermoclines. In fact it isuseful for identifying these underwater features which strongly affectthe habits of fish.

It does not require batteries or other sources of power. It is verydurable and small in size which allows storage along with other fishingequipment, such as lures, hooks, corks etc., in a fishing tackle boxmaking it always readily available. The device is not harmed nor itseffectiveness diminished if it drops into the mud, sand etc.

After one use it is immediately ready to be used again and again. Thisis very desirable since a number of measurements may be necessary toidentify the optimum area in which to fish. The device disclosed withinuniquely provides all of the above features.

The problem in measuring temperature in order to identify the optimumwaters for fishing is best described by using an example.

Suppose it is desired to catch rainbow trout in a lake 200 feet deep.From the literature it is known that the optimum temperature for rainbowtrout is 61 degrees Fahrenheit. If one were to attach a normalthermometer to a line and lower it into the water looking for the depthwhere the water temperature is closest to 61 degrees Fahrenheit aproblem would occur. It would be impossible to bring the thermometerback up to the surface and read it before the reading changes. Thethermometer might have read 61 degrees Fahrenheit at that particulardepth but it would warm or cool by the intervening water and air betweenthe depth of measurement and the fisherman.

Alternatively, one could employ a thermocouple and battery powered gauge(see DICUSSION OF PRIOR ART above). However these are cumbersome,limited by the length of wire, subject to corrosion of the gauge etc. Inaddition these devices are very expensive.

The present invention works in the following way.

A tape containing a temperature sensing component, such as a liquidcrystal ribbon, is used to measure temperature. This tape is encased inenough clear resin (plastic) to control heat flow but not too much inorder to avoid undesirably long thermal equilibration times.

This device is lowered into the body of water to be fished. Preferablythis is done by attaching the device to the line of a normal fishing rodand reel and then lowering or casting it into the water as would be donenormally with bait or a lure. After sufficient time has been allowed forthe device to thermally equilibrate, from about thirty seconds to aboutfive minutes depending upon the exact design, the device is quicklyretrieved and the temperature is read. The fact that a reel is usedmakes retrieval almost trival since there is no loose line to deal with.

This measurement is easy to make and can be done reliably since theresin provides sufficient insulation and hydrophobicity so that thedevice holds the temperature for at least several minutes in the airwhile it is being read by the fisherman. At least one thirty-second(0.03) of an inch and preferably at least one sixteenth (0.06) of aninch of insulating plastic should be provided between the temperaturestrip and the liquid of which the temperature is being measured, so thatthe intervening water between the depth of the water measurement and thesurface doesn't change the reading in the time it takes to retrieve thedevice (normally less than one minute). The hydrophobic nature of thedevice prevents wetting by water. This prevents sudden cool off of thedevice by flash evaporation when the device is raised into the air fromthe water (wind chill).

FIG. 7 illustrates the use of the present invention in a fishing lure.In this embodiment the fishing lure is indicated in the drawings at 300.The fishing lure comprises a fishing lure body (217) made of matrixmaterial described herein above of sufficient thickness to insure thatthe temperature will remain at the temperature that is read by the lurebelow the liquid surface and is sufficiently thin to allow thetemperature to be obtained in the bath in a reasonable period of time.Included within the body are reflecting or colored areas (215) toattract fish. Depending from the body portion is a hook member (214)connected to the body portion with a connecting element (217a). Aconnecting element (216a) at the front of the lure allows attachment ofthe fishing line (216) which is connected to a fishing reel (not shown).At the rear of the lure as an optional feature a fin (218) may beprovided and have attached thereto a second hook (214a).

The temperature sensing element (200) located within matrix (217) mayinclude a graduated scale (302) and color portions (304) which changecolor depending upon the temperature which is obtained at a given depth.

FIG. 8 illustrates the use of the device as a trap or net. The surfaceof the lake or pond is indicated at (201). A float (202) is providedhaving a depending line (209) attached thereto. The line in turn isattached to a trap (213). The trap includes walls (214) and atemperature sensing device (200) as described herein above. Fish (203)are seen adjacent the trap and one fish (204) has been trapped therein.The walls (214) includes a contour (313) to guide fish into the trap andmake exit difficult. The direction of the flow of the water in thestream is indicated at (205). A sinker (208) is attached to the trapwith line 209 to ensure its location below the surface (201) of thepond. The length of line 201 may be varied to ensure that the trap isset at a desired depth above the bottom which has been determinedthrough the use of the temperature sensing device (200).

FIG. 9 illustrates use of the device in connection with a rot line. Thesurface of the pond or lake is indicated at (201). A line (212) isattached to a tree T located on an adjacent bank B. A float (202) hasdepending therefrom a line (202a). Suspended between the lines 212 and202a is a trot portion 206 having depending therefrom a series of lines207 and hooks (207a) attached thereto. Also depending from the line(206) is the temperature sensing device (200) described herein above.The bottom of the lake or pond is illustrated at (211). The trot line isprovided with sinkers (210) which ensure that it will located below thesurface. Fish (203) are seen within the pond. The fish (204) is about totake the bait and be caught through one of the hooks (207a).

F) Preparation of Temperature Measurement Devices of the Invention

This section provides some of the general procedures and considerationswhich bear on the actual preparation of suitable devices of theinvention. This information in no way implies, or should be construed toimply, limitations on the design of the device. The procedures given areby no means the only way such devices can be prepared. Other methodswill be obvious to one skilled in the art of plastics processing andmolding.

Unsaturated polyester resins were used to prepare the devices in thePREPARATION METHODS section given below. Suitable resin can be obtainedthrough retail outlets as "CLEAR LIQUID PLASTIC CASTING RESIN" availablefrom Chemco Resin Crafts Co. of Dublin, Calif. 94568 (stock no. 00183).Another such resin is "ENVIRO TEX CASTING RESIN" from EnvironmentalTechnology Inc. of Fields Landing, Calif. 95537 (stock no. 5032). Athird example of a suitable resin is GLASS-KOTE Clear Casting Resin fromPlastic Sales and Manufacturing Co. Inc. of 3030 Cherry St., KansasCity, Mo. 64109.

A suitable catalyst for these polyester resins is methyl ethyl ketoneperoxide. MODERN PLASTICS ENCYCLOPEDIA reference 4a, pages 160-162discusses the available peroxides and their use. Methyl ethyl ketone wasused in the preparations discussed below since it is excellent for roomtemperature applications. This material is also known as a hardener andis also available from Chemco Resin Crafts Co.

As discussed previously, many plastics are suitable and can be chosen tooptimize performance for particular applications. Each resin has uniqueuse and handling procedures. These are thoroughly described in the priorart.

Background references 4a-c adequately discuss resins and their handlingand processing techniques for converting them to plastics. Thesereferences are also very useful in identifying suppliers for theseresins and other materials involved in plastics production.

These same references contain copious amounts of physical and chemicalproperty data on resins and the plastics derived from them. This data isvery useful for the identification of resins which can be used to matchthe physical and chemical properties of the plastics to the specificapplication of the device. Examples of such properties include opticalclarity, weather resistance, ease of molding, compatability withinformation inserts and thermometer strips (e.g. melting point, curetemperature, mutual insolubility), chemical resistance to the liquid inwhich temperature measurements will be made.

Examples of properties which need to be considered in matching a deviceto a particular application are transparency, durability, a densitygreater than the liquid in which a temperature measurement is to bemade, and a non-wetting and inert surface to prevent wind chill typecooling effects when the device is raised from the liquid. Therefore ahydrophobic surface is needed if the liquid is aqueous and a hydrophylicsurface would be desired for measurements in nonpolar liquids such asgasoline, fuel oil, oil or petroleum.

Another property needed of the plastic is low thermal conductivity. Allof the plastics mentioned above have adequately low thermalconductivity. Plastics filled with conductive fillers. for example withnickel powder, would not be desriable if the level of filler was greatenough to impart electrical conductivity to the plastic. Good corrosionresistance to the medium the device is to be used in, and the ease ofprocessability in preparing the device are also desirable properties ofthe plastic.

Below are listed procedures which were used to prepare devices accordingto this invention.

The unsaturated polyester resins described above were used in thepreparations. Unsaturated polyester thermoset resin is composed ofpolymers of phthalic anhydride, maleic anhydride and glycols in styrenecopolymer and solvent. Styrene usually composes about 45 to 50% of thetotal by weight. The version referred to as "gel coat" is the mostpreferred. The peroxide catalyst initiates the free radicalpolymerization chemical reaction which causes the styrene to polymerizeand crosslink the unsaturated polyester causing the entire mass toharden to a clear and colorless thermoset plastic.

Preparation Method A is for the use of liquid crystal ribbon or coilspring temperature sensors. Preparation Method B is for the use ofliquid in glass temperature sensors with a low maximum temperature.

Preparation Method B is most suitable in situations where there is someconcern that the component within

Almost all of the line (20) is pulled through the hole (16) from the topof the tube. A knot (24) placed near the end of the line (20) below thebottom (16) of the tube prevents the end (26) of the line from goingthrough the orifice (16) of the tube. Another knot (28) is tied on theline close to and outside of the orifice (22) of the tube. The line (20)is then taped down onto a surface (30) with tape strips (32) and (34).

A liquid crystal thermometer (36) containing desired information such asa list of optimum temperatures for game fish (38) and (40), is placedupside down under the line. The information strip (38) and (40) andthermometer (36) are glued to the line (20) at a distance up from thesecond knot (28) such that they will be recessed into the resin when thesecond knot (28) is pulled to the hole (16) in the bottom of the mold(10). Scotch tape can be used instead of glue or the glue may be as anadhesive on the temperature and/or information tape(s). The tapes (32)and (34) are removed enabling the thermometer (36) and information tapes(38) and (40) to become mobile. the matrix may not withstand thetemperatures encountered in a rapid cure of the thermoset or inthermoplastic processing.

Preparation Method C and D are more suited for mass production.

1. Preparation Method A

The setup arrangement used for Method A is shown in FIG. 1. A sixtymilliliter tapered polypropylene round tube (10), with a inside diameterof 1.014 inch at the bottom and 1.065 inch inside diameter at the topwith a conical bottom (12) and a cap (14) was used as a mold. This moldproduces devices of about the above tapered thickness and 4.20 inchestotal length with the conical portion equaling 0.563 inches of thislength.

One pinhole (16) was drilled in the bottom of the tube and one pinhole(18) in the center of the cap. About two feet of monofilament line (20)was threaded through the hole (16) in the bottom of the tube.

The thermometer (36) and the tape(s) (38) and (40) are pulled into themold (10) using the line extending from the bottom hole (16). A thirdknot (42) (FIG. 2) is tied in the line (20) on the outside of the bottomof the mold and next to the mold to support the mold subsequently and tostopper the pinhole (16) to prevent resin leakage.

A sufficient amount of the CHEMCO unsaturated polyester resin, describedabove, was added to a mixing container. Sufficient catalyst, for examplebenzoyl peroxide or methyl ethyl ketone peroxide, is added to the resinand the mixture was blended thoroughly and poured into the mold. Toomuch catalyst and too warm a temperature has to be avoided to preventcracking of the device during curing. For the above mold, two ounces ofresin and sixteen drops (at about 0.05 ml per drop) of methyl ethylketone peroxide and a room temperature of about 65 degrees Fahrenheitwas found to give a good product.

Immediately after the catalyzed resin has been poured into the mold (10)the line (20) from the top of the mold is fed through the pinhole (18)in the cap (14) and then the cap is placed onto the mold (FIG. 2). Theline portion (42) protruding through the cap is then tied to a suitablehorizontal support being a vertical arm (46) and a base (48). The mold(10) is allowed to hang suspended in the air until it has cured(hardened). The mold is held in place by the knot (42). Hanging the mold(10 and 14) in this manner holds the thermometer straight in the mold.

Alternatively, a vacuum may be applied to the airspace above the resinto hasten the removal of trapped air which is present in the resin asbubbles introduced in the mixing step. These bubbles rise and leaveunassisted if the cure rate isn't too fast.

Depending on the resin used, the amount of catalyst used and the curingtemperature, a post cure heating may be desirable to avoid a stickysurface on the product. One half to two hours at 175 to 225 Fahrenheitis sufficient to post cure the device produced by the above procedure.Addition of activator, normally cobalt naphthenate, may be used instead,as is well known in the art.

The device is then removed from the mold by removing the cap and thenflexing the flexible plastic mold while holding the mold upside down.The molded part simply falls right out. The extraneous line and plasticare trimmed from the device [flashing].

For convenience, a hole can be drilled into the device, preferably inone end, and an eye screw to fit the hole drilled inserted to provide ahook on point for line in the use of the device (see for example FIG. 5(110)). Alternatively a hole can be drilled through the device,preferable on either or both ends of the device for line attachment.

The device is now ready to use.

Devices which use liquid in glass temperature sensing components whichhave the capability to measure high temperatures can be prepared usingPREPARATION A provided the maximum temperature experienced by the sensorduring the curing of the resin does not exceed the temperature theliquid in glass sensor can withstand before breaking.

2. Preparation Method B

The procedure used to prepare devices in which the temperature sensorwas liquid in glass with a maximum temperature reading of only 100degrees Fahrenheit was as follows (FIGS. 3A, 3B, 3C and 3D).

The temperature sensor (50) comprising an liquid (alcohol) in glassthermometer (52) mounted on a stainless steel scale (54) was obtainedfrom PENN PLAX INC. (Garden City, N.Y., 11530), cat. no. T-SS. Thisthermometer is designed to measure temperatures over the 30 to 100degrees Fahrenheit range. A stainless steel hook (not shown) was removedfrom this unit so that no heat conducting metal would protrude from thefinished device (FIG. 3D).

The device was prepared in three steps. The first step (FIG. 3A)comprised mixing 20 drops of methyl ethyl ketone peroxide catalyst intofive ounces of ENVIROTEX casting resin described previously. Thismixture (58) was poured into a rectangular (5"×3"×1") mold (56). Whenthis resin hardened sufficiently to easily support the weight of thetemperature sensing component step 2 was performed.

In step 2 (FIG. 3B) the temperature sensing component (52) is placedonto the harden resin (58) prepared in step 1 (away from the edges). Asecond layer of resin (60), prepared by mixing only ten drops ofcatalyst with five ounces of resin, is poured over it. The lower use ofcatalyst slows the cure rate which prevents the temperature frombecoming too high which could break the temperature component. The curerate of this layer can be very slow. Slight warming markedly enhancesthe cure rate. Caution is required if any heating is used since itcannot exceed the usually very mild temperature temperature maximum ofthe liquid in glass thermometer, of about 110 degrees Fahrenheit in thiscase, which is the limit of the temperature sensor before it may break.Temperature sensors designed for higher temperatures will allowcorresponding higher cure temperatures. A safer method is to performstep 3 after the second resin layer becomes firm. Step 3 (FIG. 3C)consists of placing a thin layer (62) of highly catalyzed resin,prepared as in Step 1, on the second layer while it is still tacky. Thislayer cures quickly producing the desired hard surface and promotes thecomplete curing of the second layer (60 FIG. 3B). Since the third layer(62) is thin not much heat is produced. The third layer need only be asthick as the thinnest pourable layer can be, about 1/16"-1/8" or less.The finished device (50) is shown in FIG. 3D and consists of atemperature sensor (52) with a scale (54) embedded in a cleartransparent matrix (64).

3. Preparation Method C

Devices representing the invention can be prepared using the moretraditional method of casting plastic parts using a metal mold (FIG. 4)so long as certain modifications are implemented to accommodate theinclusion of the temperature sensing element.

An aluminum mold (80) was prepared in the usual fashion of pouringmolten aluminum onto the desired mold shape made out of sand. This moldcontained ten cavities (82) and consisted of two sections (84 and 90).The bottom half of the mold (84) (FIG. 4a) contained ten cavities, eachpolished to a mirror-like finish and of the dimensions of 0.95" width by0.48" depth by 4.6" long. The cavity can be any shape so long as itadequately encloses the temperature sensor to be added latter and allowsremoval of the device from the mold after casting.

The top half (90) (FIG. 4b) was identical to the bottom half except thatslots (92) were cut in the top of the cavities which open the cavitiesto the air when the mold is assembled. These allow the introduction ofthe resin and escapage of trapped air. The cavities were polished to amirror finish to impart a smooth glass-like finish to the device forgood transparency.

This mold was used in the following manner. The bottom half (84) waslaid flat and filled to about half with three ounces of catalyzed resinprepared from the GLASS-KOTE clear casting resin discussed previously.Clear green colorant was blended with the resin along with the catalystto impart a pleasing clear blue color to the finished device. In usingcolorant it should be obvious that too much should not be added whichcould impair the reading of the temperature sensor.

After the resin thickens, the temperature sensor (96) is laid onto thesurface of the partially cured resin. Only the positioning of one of theten temperature sensors is illustrated in FIG. 4A.

A preferred procedure (FIG. 4C) is to first attach a 1/2"×4"×0.015"liquid crystal thermometer sensor (102) to one side (103) of a1/2"×1/2"×4" acrylic rod (104). Useful information is then attached toone or more of the other sides. The ends of the rod were not usedalthough they could be. This rod (104) containing the temperature sensor(102) was then laid onto the partially cured resin (108). A usefulfeature of the Procedure is that the square rod can easily be placedanywhere within the mold cavity (82). This can be used to position theattached liquid crystal temperature sensor at different locations toyield devices with a range of temperature response properties. Thecloser the temperature sensor is located to the edge of the mold cavitythe thinner will be the layer of cured resin and therefore the fasterthe devices' temperature response will be. This is a useful method forcontrolling the temperature response properties of the device.

Once the temperature sensor has been positioned, the top half (90) ofthe mold (FIG. 4b) is added. The mold is clamped to prevent slippage.Catalyzed resin is then poured through the slots (92) until each moldcavity is full. It is useful to exercise care in pouring the resin toavoid trapping air. The resin is then allow to cure or harden.

After hardening, the devices (FIG. 5 (100)) (ten devices for the moldillustrated in FIG. 4) are removed, de-flashed if necessary, and a eyescrew (110) added at a suitable spot to facilitate the attachment of aline during use. FIG. 5 illustrates a finished device (100) preparedaccording to this procedure. As shown, information (106) on the optimumtemperatures for some fish were included to facilitate the use of thedevice for fishing.

4. Preparation Method D

The preferred method used to prepare the devices of this invention wasto use individual cylindrical polypropylene molds (FIG. 6A (116)). Thisprovides a quick, flexible and simple method of device preparation inlarge quantities. This polypropylene mold (116) is a tube having alength of 4.5" and a diameter of 1.1" (124) just above a 0.6" highconical base (118) and 1.15" diameter at the top (122). The slight taperaids in removal of the molded part.

A 1/2" square acrylic rod (FIG. 6B (104)) was cut to a length of fourinches and the ends were polished. A hole was drilled into the center ofone end of the rod (104) using a #51 drill bit. A C20 eye screw (110)(NETCRAFT CO.) was screwed into this hole such that 3/8" of the shankremained outside of the rod. This spacing is important for positioningthe insert as described below.

A liquid crystal temperature sensor (102) is attached to one side of therod using glue.

Any other desired information is then attached to the other sides of therod (106).

Catalyzed GLASS-KOTE resin with colorant is slowly poured into the mold(116) to just over half full. The insert containing the temperaturesensor (Entire assembly of FIG. 6B) is placed into the resin slow enoughto avoid trapping air bubbles. The eye screw (110) provides a handle forpositioning the temperature sensor at the location in the mold for thedesired temperature response of the device.

Once positioned enough additional resin is added to top off the mold andcompletely cover the insert. The final liquid level should lieimmediately beneath the ring of the eye screw. This mode of introducingthe eye screw has the added advantage of being very secure. It can bedifficult to obtain a firm screw setting in highly crystalline thermosetplastic.

After the resin has substantially cured, the device is easily removedfrom the mold and is ready for immediate use. FIG. 6C illustrates thefinished device.

III. EXAMPLES

The following examples serve to illustrate how the device of theinvention is used to measure temperatures. These examples are forillustrative purposes only and in no way should be construed to implylimitations on the invention.

EXAMPLE I

The effectiveness of the device from EXAMPLE I was tested as follows.

Into a pan of lukewarm water (95.4 degrees Fahrenheit) was added adevice prepared according to METHOD A which weighed 60.17 grams with atotal volume displacement of approxamately 55 milliliters and dimensionsof 1.014 inches thick at the bottom, and 1.065 inches thick at the topwith a conical bottom of 0.563 inches in length and with a total overalllength of 4.20 inches. A stopwatch was started at the same time. Thisdevice required seven minutes for the temperature to rise from less than66 degrees Fahrenheit to 82 degrees Fahrenheit.

At this point the device was removed from the lukewarm water and intothe air under a light cool breeze of about 66 degrees Fahrenheit. Thedevice was not dried off.

The temperature recorded by the device remained at 82 degrees Fahrenheitfor four minutes then started to drop very slowly (about one degree perthree minutes). This is plenty of time for a person to read thetemperature.

EXAMPLE II

In a comparison test, a liquid mercury thermometer was tested in thesame manner and under the same conditions as the device of thisinvention used in EXAMPLE I. Mercury thermometers are well known in theart. The one used in this test had the demensions of 5.583 inches totallength, 0.259 diameter, 0.638 inches mercury bulb length, 0.428 inchescapillary length and covering the temperature range of minus ten to onehundred and ten degreec Celsius and readable to about 0.2 degreesCelsius.

In this test it was found that the temperature reading immediately fellupon removing the thermometer from the bath thereby preventing the bathtemperature from being read in this manner.

Therefore it can be concluded that only surface temperatures can bemeasured using a normal thermometer and even then it has to be heldbeneath the water while the temperature is being read.

EXAMPLE III

Another device was prepared using METHOD A except that a smaller moldwas used (three and one-half inches long and five-eights inches thick).This resultant smaller device has a thiner plastic layer covering thetemperature sensor As will become clear below, it was found that thinnerplastic layers provide a faster response time than devices with thickerplastic layers.

This device was tested under the same conditions as in EXAMPLE I. Theresults were (1) that the device was warmed to eighty degrees in lessthan two minutes. (2) When the device was removed from the bath into theair the reading remained at eighty degrees Fahrenheit for five minutes.This is excellent performance since very little time was needed forthermal equilibration and yet the device held the temperature for plentyof time for the user to withdraw the device from the water and read it.When taken with EXAMPLE I this demonstrates that the temperatureresponse times can be controlled by varying the thickness of the plasticlayer between the temperature sensing component and the liquid in whicha temperature measurement is to be made.

EXAMPLE IV

This EXAMPLE illustrates that all combinations of liquid crystaltemperature sensitive tape and resin are not useful for the presentinvention.

Two molds, illustrated in FIG. 3, of the dimensions, one and one halfinch by three inches by one half inch, was filled half way withcatalyzed polyester resin. One mold was made of latex and the other ofpolypropylene. Temperature tapes covering the range of 86 to 98 degreesFahrenheit were laid on the resin in each mold when it had substantiallyhardened. Both molds were then filled with catalyzed resin. Thetemperature tapes drifted up near the surface during the curing processso that only a fairly thin film of about 0.01 inches of resin residedbetween the tape and the air. Both of these devices were found to coolquickly, within a few seconds, on lifting them out of warm water at 98degrees Fahrenheit into air at room temperature. At least about 0.03inches and preferably about 0.10 inches of resin should reside betweenthe air and the temperature sensor.

EXAMPLE V

This EXAMPLE illustrates that the device is useful for measuring thetemperature of bodies of liquid in which the usual temperature measuringmethods would either fail or would be very difficult to implement. Thedevice used in this test was prepared according to METHOD B.

It was desired to measure the temperature at the bottom of the MissouriRiver near St. Charles, Mo. in January. This river at this location isfilled with suspended solids (silt) making the water opaque and withdrifting ice flows. The bank of the river was covered with thin icewhich prevented any close approach to the water. For the reasonsdiscussed previously, this temperature measurement could not be madeusing normal liquid in glass, liquid crystal, bimetallic strip or liquidexpansion based thermometers. The use of a thermocouple device would behighly impractical and expensive as discussed previously. A device ofthis invention prepared according to METHOD B measuring 5.862 incheslong 2.876 inches wide and 0.975 inches thick with a 4.23 inch longalcohol in glass temperature sensor covering the temperature range of 30to 100 degrees Farhenheit centrally positioned in it, was merelyattached to the line of a fishing pole and then cast into the river atthe desired location for the measurement. The water was flowing rapidlyand was about three feet deep. The device was allowed to lie on thebottom of the river until thermal equlibration was attained asdetermined by repeatedly quickly removing the device from the water andreading the temperature from the scale associated with the temperaturesensing device imbedded within the device. These readings did not varywidely but showed the desired smooth decrease with time. Thermalequilibration was reached at 37.0 degrees Fahrenheit when thetemperature reading no longer dropped with time.

The device was then pulled from the river and the temperature wasfollowed with time to record how well it retained the temperaturereading of the bottom of the river.

The data obtained are given in Table I.

                  TABLE I                                                         ______________________________________                                        Temperature response data for the device                                      tested in EXAMPLE I.                                                          TIME (minutes)                                                                           TEMPERATURE (degrees Fahrenheit)                                   ______________________________________                                        2          37.0                                                               3          37.0                                                               4          37.2                                                               5          37.2                                                               6          37.0                                                               7          37.0                                                               8          37.2                                                               9          37.2                                                               10         37.2                                                               11         37.4                                                               ______________________________________                                    

It is clear from Table I that excellent temperature stability wasachieved with the device despite the harsh environment the reading wasmade in.

EXAMPLE V-A

The device used in EXAMPLE V held the 37.0 degrees Fahrenheittemperature reading for about one minute in sunlight. Of course this isstill plenty long for a user to make a reading. However, if is desiredthat the device hold a reading for a long time it is preferred that thedevice be shielded from direct sunlight when sun radiation-absorbingplastics are used to prepare the device.

Since this device was made of unsaturated polyester resin it isimportant to shield it from the sun for the long period of the testsince this resin strongly absorbs ultraviolet light from the sun. Thiscan cause a significant warming rate.

EXAMPLE VI

The same device used in EXAMPLE V was used to measure the temperature ofthe Meramec River near Kirkwood, Mo. The river contained much loose iceand it was desired to measure the temperature of the bottom of theriver. The device was lowered into the river using monofilament line asin EXAMPLE V. The device was allowed to thermally equilibrate as inEXAMPLE V also. The water depth was about five feet. Table II lists theresults obtained when the device was pulled from the river for reading.It is clear from this data that the device held the temperature of thebottom of the river for at least several minutes. This is plenty of timefor the user to record the temperature.

                  TABLE II                                                        ______________________________________                                        Temperature response data for the device                                      tested in EXAMPLE II.                                                         TIME (minutes)                                                                           TEMPERATURE (degrees Fahrenheit)                                   ______________________________________                                        0          35.2                                                               2          35.2                                                               4          35.0                                                               7          33.5                                                               ______________________________________                                    

EXAMPLE VII

A device was prepared using METHOD B and a simple rectangular mold (FIG.3). The temperature sensing component was a liquid crystal tapesensitive over the 66 to 86 degrees Fahrenheit range instead of theliquid-in-glass thermometer shown in FIG. 3. A high cure rate waspossible since the liquid crystal ribbon is very stable at the high curetemperatures.

The final device measured one and one-half by four by three quarters ofan inch. This device was equilibrated in lukewarm water at 86 degreesFahrenheit. About four minutes were needed for this equilibration.

On removing the device into the air at 66 degrees Fahrenheit the deviceheld the 86 degree reading of the bath for at least four minutes andonly changed to 85 degrees after five minutes.

EXAMPLE VIII

A device was prepared according to METHOD B containing an alcoholtemperature sensing component.

This device measured two and three-fourths by five by one inch. Thisdevice was placed in a bath of water at 44 degrees Fahrenheit. Thisdevice held the temperature reading of the bath, 44 degrees Fahrenheit,for five minutes after removing it from the bath.

This is plenty of time to enable a user to read and record thetemperature.

EXAMPLE IX

A device was prepared using METHOD B and a bimetallic strip as thetemperature sensing component. The dimensions of this device was thesame as that used in EXAMPLE VIII. This device required a fairlylengthily thermal equilibration time of about twenty-five minutes in awater bath at 86 degrees Fahrenheit. This was probably because of theinsulating air gap around the bimetallic strip. This device held the 86degrees Fahrenheit bath temperature for at least five minutes onremoving it from the bath.

This demonstrates the usefulness of this device for these types ofmeasurements.

EXAMPLE X

This example illustrates how the device is used to aid in catching fish.At the lake of the Ozarks, Mo. the water temperature in the summerreaches about eighty degrees. A catch of two to four bass per day isnormally a good catch. On a particular day the water temperature was 82C. and no fish were encountered even after about six hours of fishing.The device prepared according to Method C was used to find water of theoptimum temperature for bass (71 C.). This water was found near themouth of a small spring fed stream entering the lake. In twenty minutessixteen bass were caught by just one fisherman using artificial bait andjust one rod and reel. Equivalent success was had by four fishermen inanother boat very close (about fifty feet) nearby.

What is claimed is:
 1. A fishing lure comprising:a body portion formedin a contour to simulate bait for fish; a measurement portion integralwith said body portion, and including a temperature sensing deviceincluding a temperature sensing element imbedded a distance of at leastabout 0.06 inches within a matrix made of thermally insulating andnon-wetting material; and hook means for engaging a fish attracted bysaid body portion, whereby a temperature read by said temperaturesensing device at a selected depth will be maintained by said matrixmaterial as said lure is retrieved and the temperature at the selecteddepth is read.
 2. A fishing lure according to claim 1 wherein saidsensing element is imbedded a distance of at least about 0.1 incheswithin said matrix.
 3. A fishing lure according to claim 1 wherein saidlure contains graduated means for indicating the temperature read atsaid selected depth.